Jones — On Common and Roseate Terns. 37 



clear that two females had laid to the same nest. This was 

 proved by the marked difference in the degree of incubition of 

 two or three of the eggs from the rest in the nest, or by the 

 marked difference in size and markings and textnre of the 

 shell. In a relatively small proportion of cases nests contain- 

 ing fonr eggs were clearly mixed sets. While many nests 

 contained but one egg, T never met with a case where the single 

 egg could be regarded as a nest complement. Either another 

 or other eggs were laid in the nest later, or the nest proved to 

 be deserted, or the egg was infertile and remained after the 

 others had hatched. The usual number of eggs or young was 





COMMON TERN. (Sterna Hirundo.) 

 Egg. Young Just Hatched, Young Two Days Old. 

 Woepecket Id., Mass. 



